CSC336 Final (Exam I) 2
Terms in this set (39)
Hypertext Transfer Protocol
Used by a web client to communicate with a web server
It is stateless and connection-oriented
File Transfer Protocol
Copying files between a host and a remote machine
Simple Mail Transfer Protocol
Delivering email messages
Domain Name Server
Converting a domain name to an IP address
Hypertext Markup Language
Used for developing a web document
Post Office Protocol v3
Accessing email messages with limited functions
Internet Message Access Protocol
Accessing email messages with more user options
A service that requires a connection startup phase prior to data exchange
A service that does not require a connection startup phase prior to data exhange
The boundary of two adjacent layers
Defines what operations/services the lower layer makes available to the upper
The boundary of two peer layers
Defines the rules that the peer layers must follow to achieve communication
Application - Service - Protocol
Web Browsing - Web Accessing - HTTP
FTP - File Transferring - FTP
Email - Email - SMTP, POP3, IMAP
DNS - Domain name translation/conversion - DNS
What are the names of the PDUs for the five layers of TCP/IP? (Bottom layer to top layer)
Physical - Signal/bit
Data Link - Frame
Network - Datagram/Packet
Transport - Segment
Application - Message
What are the two required addressing elements for a TCP client to request a connection? Name them and what they are used for
IP address and Port ID
IP address indicates the host
Port ID indicates the application server
Together they indicate an application running on a machine
In-Band Control vs Out-of-band Control (Definition + Example of application layer protocol)
Out-of-band Control sends command and data separately using two links, In-band control sends with one connection
FTP uses Out-of-band
HTTP uses in-band
How many email servers are involved in an email service using SMTP? What is the usage of SMTP? What is the usage for both POP3 and IMAP?
There are two email servers involved in SMTP, the local and remote server. SMTP is for delivering mail only, it cannot access mail. The mail client gives the mail to the local SMTP server, which then connects to the remote SMTP server and delivers it there.
POP3 and IMAP are used for accessing mail, and they can do so by accessing the remote server from a client.
What is an ephemeral port? What application layer protocol uses this?
A temporary port used by FTP.
Created by the FTP client to receive data from the FTP server
Disconnects once data exchange is done
Static Web Pages (Definition + Example)
Predefined web pages, usually by a markup language such as HTML
ex - Dr. Yang's class site
Dynamic Web Pages (Definition + Example)
Web pages that are generated by the server after a request has been made.
ex - Online Banking
The set of all web pages
A page that may contain links to other pages
Text + Tags
User Resource Locator
Consists of 4 things:
- Domain name
- Application Port ID
- Web page location + name
Problems with HTTP/1.0
1. Performance - consistently establishing TCP connections is costly
2. Stateless - Server does not maintain information on the client so it ignores things such as multiple calls to the same page
What are 2 problems with HTTP/1.0 and 2 solutions proposed in HTTP/1.1?
Performance - Persistent Connection - Connection is maintained even after request has been serviced, disconnects only after connection has been idle for a while. This limited the amount of TCP openings/closings, boosting performance.
Stateless Protocol - Cookies -Collect info on the client and the client's state
Protocol Data Unit
Represents the bits that include the headers and trailers for that layer, as well as the encapsulated data.
What is a socket interface?
The set of API's used for the communication between an application and TCP or UDP
What is the execution sequence of a server and a client?
The server program/machine must be started PRIOR to the client program/machine
What is an IP address used for?
Identifying a host
What is a Port ID used for?
Identifying an application server
HTTP vs FTP (Similarities)
1. Both defined for copying files
2. Both running on top of TCP
HTTP vs FTP (Differences)
1. HTTP uses one TCP connection to send data and commands (In-Band Control)
2. FTP uses two TCP connections: (Out-of-Band Control)
HTTP vs SMTP (Similarities)
1. Both are used for transferring files
2. In-Band Control
HTTP vs SMTP (Differences)
1. SMTP is a push protocol
2. SMTP included all responses with text and images in one response message; HTTP sends each object in one HTTP response message.
SMTP Order of Operations
1. Mail client application interacts with local SMTP server to initiate delivery
2. When the user clicks send, the application prepares a PDU (message) with this information in the email
3. Message is stored in the SMTP server and application disconnects
4. SMTP local server connects to SMTP remote server and transfers the message
The Physical Layer
1. Layer that interacts with the real world
2. Specifies how to transmit bits across different kinds of medium as electrical (or other analog) signals.
Ex. 100BASE-T, 802.11n
Data Link Layer
1. Delivers data across some physical network (typically a LAN).
2. Responsible for error checking transmissions
1. Holds entire architecture together by providing routing and addressing for packets (deliver IP packets where they are supposed to go)
2. Defines an official packet format/protocol called IP (Internet Protocol), and each host computer should have a different IP address.
Ex. IP, ICMP
1. Allows peers on source and destination hosts to carry on a conversation.
2. Two transport protocols are defined here: Transmission Control Protocol (TCP) and User Datagram Protocol (UDP).
Ex. TCP, UDP
1. Provides services to the application software running on a computer
2. Contains all the higher-level protocols
3. Does not define the application itself, it defines services that applications need
Ex. HTTP, SMTP, DNS, FTP, DHCP, IMAP, POP, SSL
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